First of all, that is a nice stack, I like a lot, wish I could find a load of cogs and spare watch part around to do something like this.. Love the large clock face, give the shot a real punch. Well done.
I use Zerene stacker and have to say I don't have a lot of issues with memory, for the close ups I've been processing I have to use a cropped sensor, due to vignette issues, however these are still large files and I've stacked over 200 images in one stack without issue, but I do have a fastish laptop with 8gb of ram, I do know people with less powerful machines and still done have problems, they just take longer to process.
I do the basically the same as bb123 however I load my raw into photoshop raw, sync my stack and save out as tiff file and run those through Zerene Satcker, normally I use PMax, and slowly venturing into DMap, I have to say it's a powerful program and just for easy stacks at the moment just use align all images and then run PMax, and save output tiff, that's how I do most stacks at the moment. There are other stacking programs around to try, a free one is CombineZP